Offset liner for a cavity charge projectile



; Nov. 16, 1965 M. A. PAUL ETAL 3,217,650

OFFSET LINER FOR A CAVITY CHARGE PROJECTILE Filed Feb. 28, 1952 2 Sheets-Sheet 1 IN VE/V TORS! MART/N A. PAUL A 01 05 6 PAUL //V6 zflm ATT'YJ -Nov. 16, 1965 M. A. PAUL ET AL Filed Feb- 28. 1952 2 Sheets-Sheet 2 UALMOD/F/ED CONE a C I E 4 k 2 550701? CONE g --X-- E \\'/4s0r0R con/5 5 3 Q\@ SPEED OF ROTATION RPS 0 TRUMPET SHAPE BEFORE OFFSET INVENTORS:

MART/N A. PAUL ATT'YS United States Patent 3,217,650 OFFSET LINER FOR A CAVITY CHARGE PROJECTILE Martin A. Paul, Endicott, N.Y., and Linus C. Pauling,

Pasadena, Calif., assignors to the United States of America as represented by the Secretary of the Navy Filed Feb. 28, 1952, Ser. No. 273,872 Claims. (Cl. 102-56) This invention relates to improvements on high explosive shells; and is directed more particularly to an improvement of the structure of the cavity liner for a spinstabilized explosive shell of the cavity-charge type in order to improve its penetrating capabilities.

Although there are numerous well-known methods for stabilizing gun-ejected explosive shells in flight, the method generally considered most desirable for over-all simplicity and effectiveness is the method which imparts rotation or spin to the shell to stabilize it. It has been discovered, however, that the spin or rotation of a shell containing a cavity charge materially decreases the penetrating capabilities or such a shell as compared with results achieved when the shell is not rotated.

This deleterious efiect of rotation on the penetrating power of cavity-charge explosive shells has limited the usefulness of many munitions utilizing this principle. Even at relatively low velocities, the penetrating power of a spin-stabilized shell containing a cavity charge amounts to but 50 percent of its non-spinning performance. It is thus of considerable importance to find some means of preventing this effect of reduced penetrating power due to shell spin.

Accordingly, the instant invention has as its primary object the improvement of the penetrating power of a spin-stabilized, cavity-charge explosive shell.

Another object of the instant invention is in providing a new and improved cavity-charge explosive shell having greater penetration power and which is of relatively simple construction.

Another object of the instant invention is in providing a new method of shell projection which increases the penetrating power of a spin-stabilized shell.

One feature of the instant invention is in providing an oflFset liner for projectile utilizing the cavity-charge principle.

Another feature of the instant invention is in providing an oifset liner for a cavity-charge projectile having a plurality of offset plane sectors where the amount of offset increases gradually from the apex to the base portion thereof.

Still another feature of the instant invention is in providing an offset liner for a projectile using a cavity charge comprising a number of sectors which are canted slightly relative to one another.

Another feature of the instant invention includes the method of spinning a projectile having an offset liner for a cavity charge in a direction such that the offset portion faces in the direction of rotation of the shell.

Other features and objects of the instant invention will become apparent upon making reference to the specification to follow and the drawings wherein:

FIGURE 1 is a cross-sectional view of the nose end of a cavity-charge type projectile; and

FIGURES 2a and 2b are plan and perspective views respectively of one embodiment of the instant invention utilizing an offset cone cavity liner.

FIGURE 3 is an enlarged right cross-sectional view of the cavity of the liner taken along line 33 of FIGURE 2b.

FIGURE 4 is a right cross-sectional view, similar to "ice FIGURE 3, of another form of the cone-shaped cavity liner.

FIGURE 5 is a graphical diagram showing the results of a penetration test performed on cavity liners of the type shown in FIGURES 3 and 4.

FIGURE 6 is an enlarged cross-sectional view of a small portion of the cone shown in FIGURE 2b.

FIGURE 7 is a cross-sectional view of a trumpet-shaped liner before being sectioned and canted.

FIGURE 8 is a perspective view of a trumpet-shaped cavity liner forming another embodiment of the invention after being quartered and canted.

A cavity liner is shown in FIGURE 1 associated with other elements of a cavity-charge type projectile which is old and well known in the art. Only the nose portion of such a projectile is shown in FIGURE 1, and it includes a body or casing portion 2 filled with an explosive mixture, and a cavity liner 1 extending upward from the bottom of easing 2 in the form of a conical surface tapering upward to a point in the center portion of casing 2, and the apex of the conical surface. This conical surface closes the bottom portion of the casing 2 thereby completely enclosing the explosive within the projectile.

The present invention relates to the improvement of the structure of this conical surface or liner to improve the penetrating power of the projectile with which it is associated.

The liner 1 for a cavity-charge type projectile is constructed by dividing the conical surface into a number of sectors and canting the successive sectors slightly with respect to each other. The force exerted by the explosive in the shell on these sectors upon impact thereof compensates for the deleterious effect of the tangential motion of the projectile and its components due to its spin.

Referring now more particularly to FIGURES 2a and 2b showing one form of the instant invention, liner 1 is made of two similar semi-conical sectors 3-4 which are canted or twisted relative to one another providing two overlapping or offset edge portions 5 and 6 which increase in depth from the tip 7 of the liner to the base portion thereof as shown most clearly in FIGURE 2b. If the shell containing liner 1 is spun in the direction shown by the arrow in FIGURE 2a, the shell will have increased penetrating power over the condition where the liner is comprised of a perfect unmodified cone. If the liner in FIGURES 1-3 were spun in the opposite direction than that shown in FIGURE 20, the penetrating power of the shell containing the liner would be lessened.

FIGURE 4 shows a right cross-sectional view of a liner forming another embodiment of the instant invention and is constructed from a conical surface which has been divided into 4 similar conical sectors 8, 9, 10, and 12 rather than 2 sectors 34 as in the species of FIGURES 23. Sector 8 of this embodiment conforms to the origi nal cone while sector 9 has been canted or rotated slightly about a line bb which passes through the axis 11 of the cone at the top portion thereof so that the amount of overlap of the sectors 8 and 9 increases from the top to the base thereof. Conical sector 10 has been rotated slightly about line a-a which also intersects the axis 11 of the original cone at the top portion of head portion of the shell. Similarly sector 12 has been rotated about a line (not shown) which also intersects the axis 11 of the original cone to provide a continuous offset surface. The abutting edges of the sectors may be soldered or joined in any known manner to form a unitary structure. The various sectors can be slightly rotated about in numerous other positions if desired, the above example being exemplary only. The exact amount of overlap at a particular level of the cone is not very critical but an extreme amount of overlap may of course cause substantial overcompensation and likewise too little overlap may lead to substantial under-compensation. It is important, however, that the overlapping sectors 16-19 face in the direction of spin of the shell, and accordingly that the amount of overlap varies from top to bottom thereof.

Although the construction of the cavity liners shown in FIGURES 24 has been accomplished by first dividing an already perfect conical surface into four separate sections which are then physically twisted or canted relative to each other, it should be understood that if desired a die conforming to the shape of the finished product could be constructed and then the resultant structure could be made in a single stamping operation. As an example of structures found satisfactory, 45 degree steel cones of .062 inch thickness and sectioned in half and in quarters were respectively put together again with silver solder in such a way that adjoining edges were offset with respect to each other, the amount of offset increasing from zero at the apex to .040 inch at the base. The cones were trimmed to 1.0 inch at the base. The cones were trimmed to 1.0-inch base diameter (a size appropriate to the 57 mm. shell). FIGURE 5 discloses the results of a penetration test with the two above cone types and with an unmodified cone used as the nose portion of respective explosive shells. It can be seen that for speeds of rotation above about 130 r.p.m., the modified cones were far superior to the unmodified cones.

A theoretical analysis of the action of the offset type shell has resulted in the following equation for the condition of exact compensation for the deleterious effect of the spin on the penetrating power of such a shell:

(1) O/AU(1cos B)=21rrF where O=total area of the offset surface at a given zone of the cone surface A=total area of the cone surface at the same given zone of the cone surface in which is measured U=velocity of shell after explosion of the shell B=the half-angle at which the wall of the cone meet during collapse at the zone in question which is an angle larger than the original cone half-angle r=radius of the cone at the point in question F=rate of rotation The offset cones which were utilized in the test resulting in the graph of FIGURE were constructed such that O/A was constant from top to base. Since the angle B is essentially constant during collapse of most of cone, Equation 1 makes it evident that the left hand side of Equation 1 will be constant irrespective of the portion of the cone involved. However, the right hand side of the equation varies with r, the radius of the right section of the cone in question. Thus at a rotational speed such that the mid-portion of the cone is perfectly compensated, the base portion will be insufficiently compensated and the apex of the cone will be overcompensated. To have perfect compensation over the entire cone, the cone would have to be offset so that the ratio O/A increases from apex to base in proportion to r.

The offset cover used in the above test represented a compromise effort at compensation; since using Equation 1 it was discovered that assuming B is 45 degrees and U is 2500 m./scc. as reasonable estimates, the two sectors would be perfectly compensated at the mid-zone of the cone, where the cone radius was .48 inch, at speeds of 100 r.p.s. for the two sector cones, and 200 r.p.s. for the four sector cones. These frequencies are actually not far from the frequencies at which the observed depth of penetration reaches a maxima.

While it appears technically difficult to construct a true cone with offsets such that O/A increases in proportion to r, a different approach is to keep O/A constant by single offset as before but to vary angle B (half angle of wall collapse) in such a way that the left side of Equation 1 increases with r. This suggestion uses a trumpetshaped shell nose as shown in FIGURE 7 which has an offset and cross-sectional shape similar to that of the coneshaped nose portion shown in FIGURES 1-3.

It can be shown that a shell liner shaped like that shown in FIGURES 7-8 will satisfy the requirements of Equation 1 that (1cos B) will increase in proportion to r. The included angle there shown increases from a limited value of zero at the apex to about 96 degrees at the base. For simplicity in specifications, the walls have been described in terms of a fixed radius of curvature. This represents a good approximation to an ideal shape. If such a shell head were quartered, and the quarters canted so that the amount of offset at the base would be .045 inch, and zero at the apex (for an inner base diameter D of 1.90 inches, a wall thickness of .050 inch, a head height H of 1.81 inches and a wall radius R of 2.59 inches), substantially perfect compensation occurs at about 256 r.p.s.

It should be noted, in conclusion, that the various species of the invention above disclosed have several features in common. All of them require the offset surface to face the direction of rotation of the shell, and that there be a plurality of offset sectors where the amount of offset increases from apex to the base of the shell head portion.

It should be noted that many modifications may be made of the specific embodiment disclosed without deviating from the broader aspects of the instant invention.

We claim:

1. In the nose portion of a spin-stabilized projectile having a hollow open ended shell casing containing an explosive mixture comprising a generally round tapered partition having a wall member converging from said open end of said shell casing to a point in the center portion thereof, the surfaces of said liner within said shell casing having a plurality of olfset sectors providing overlapping edge portions facing in the direction in which the projectile is to be spun.

2. The combination of claim 1 characterized further by said overlapping edge portions overlapping in gradually increasing amounts from said point to said open end thereof.

3. The combination of claim 1 characterized further by said offset sectors forming a generally trumpet-shaped surface.

4. The combination of claim 3 characterized further by the ratio of the area of the overlapping edge portions to the area of the adjacent outer surface of said section forming the trumpet-shaped surface being a constant.

5. The combination of claim 3 characterized further by the ratio sectors forming a generally symmetrical conical surface, the ratio of the area of the overlapping edge portions to the area adjacent thereto forming the conical-shaped surface increasing in direct proportion with the distance of the conical surface from the axis of the said conical surface at the point in question.

References Cited by the Examiner UNITED STATES PATENTS 33,863 12/1861 Woodbury 102-51 760,338 5/ 1904 Kwiatiwski 1025 1 2,419,414 4/1947 Mohaupt 102-56 2,605,703 8/1952 Lawson 102-56 X FOREIGN PATENTS 554,833 7/ 1943 Great Britain.

OTHER REFERENCES G. B. Clark and W. H. Bruckner, Behavior of Metal Cavity Liners in Shaped Explosive Charges, American Institute of Mining and Metallurgical Engineers, Technical Publication No. 2158, March 1947, pp. 1-12.

BENJAMIN A. BORCHELT, Primary Examiner.

SAMUEL BOYD, Examiner. 

1. IN THE NOSE PORTION OF A SPIN-STABILIZED PROJECTILE HAVING A HOLLOW OPEN ENDED SHELL CASING CONTAINING AN EXPLOSIVE MIXTURE COMPRISING A GENERALLY ROUND TAPERED PARTITION HAVING A WALL MEMBER CONVERGING FROM SAID OPEN END OF SAID SHELL CASING TO A POINT IN THE CENTER PORTION THEREOF, THE SURFACES OF SAID LINER WITHIN SAID SHELL CASING HAVING A PLURALITY OF OFFSET SECTORS PROVIDING OVERLAPPING EDGE PORTIONS FACING IN THE DIRECTION IN WHICH THE PROJECTILE IS TO BE SPUN. 